The invention described herein relates to valves and more particularly to a check valve useful in a nuclear reactor and other fluid systems.
Conventional check valve constructions include a housing having a flow-through opening equipped with a valve seat arranged to receive a check valve disc which operates by the force of liquid or a fluid flowing therethrough between open or closed positions or somewhere between fully open or fully closed, depending on the force of the flowing fluid. The valve disc which contacts the valve seat to preclude liquid from reverse flow through the valve, contains a heavy integral portion in the center of the disc and on that side of the disc which faces the discharge outlet. A pivot arm is attached to a pin anchored to the central portion of the disc, or it is integral with the disc, while the other end of the arm is pivoted in bearing blocks mounted in the casting body, thereby permitting valve disc movement between open and closed positions to allow flow in one direction through the valve or preclude such flow in a reverse direction through the valve.
Since the valve disc is held open by the velocity pressure of liquid flowing through the valve, it is apparent that some minimum velocity will hold the valve disc open for each valve. However, unless the valve is held fully open, an additional pressure drop over that for which the valve has been designed, occurs through the valve which results in efficiency. Under these circumstances of a partially open valve, the valve also becomes unstable, valve disc oscillations occur and the pins and bearing blocks holding the valve disc wear at an accelerated rate.